feat: initial Speedboard implementation

sitespeed.io web UI with Express/Pug/SQLite — port 3132.
Includes job queue, SSE live log, full metrics dashboard,
site history, CO2/axe/CWV sections, and Docker support.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

views/error.pug

@@ -0,0 +1,7 @@
+extends layout
+
+block content
+  div(class='text-center py-20')
+    h1(class='text-4xl font-bold text-red-600 mb-4')= title
+    p(class='text-gray-600 mb-6')= message
+    a(href='/' class='bg-indigo-600 text-white px-5 py-2 rounded hover:bg-indigo-700') Back Home